Problem: Evaluate the following expression when $c = 7$ and $d = 9$. $8$ $c$ $ + 4$ $d$ $ - 5$
Solution: Substitute $7$ for ${c}$ and $9$ for ${d}$ $ = 8{(7)} + 4{(9)} - 5 $ $ = 56 + 36 - 5 $ $ = 87$